1. Field of the Invention
This invention relates to the field of exercise devices, and in particular devices adapted for swinging a pair of synchronized jump ropes, commonly called "Double Dutch".
2. Description of the Prior Art
Various devices have been conceived for swinging jump ropes. Such rope-swinging apparatus are intended to simulate the manual motion of a pair of persons facing one another and swinging a rope together in a circular arc, the rope defining a substantially cylindrical area between the persons, wider at the midpoint and narrower at the ends of the ropes. At the narrowest, the radius of the cylindrical area is defined by the swinger's arm. In use, the rope swingers begin before the jumper begins. Upon the swingers' reaching full speed, a jumper moves into the cylindrical area and, in synchronization with the swinging rope or ropes, jumps over each rope as it repeatedly goes around.
Various mechanical devices have been conceived to simulate the manual motion of the pair of persons swinging a jump rope in a circular arc. Although the required motion is quite simple for persons, the necessary motion is somewhat more difficult to accomplish using a machine. The prior art includes a number of devices employing a driven, rotatable shaft upon which a rope holding means is mounted so as to extend radially from the shaft. A first end of the jump rope is attached to the rope holding member at a point displaced from the shaft, the point defining the circular arc of the swung rope at the driven end. The opposite end of the jump rope is normally tied to a fixed point, the rope being driven only by the shaft at the first end of the rope.
The cylindrical space defined by the swung jump rope must be large enough to encompass the height of the jumper. Due to the centrifugal force of swinging the rope, the rope describes a path bowed outwards from a perfect cylinder. The rope is forced radially outward from the axis of revolution, assuming a curved shape, and accommodating the tallest jumper toward the center of the rope. When the rope is tied to a fixed point at one end, swinging the other end describes a similar area, but the dimensions of the entire encompassed area are reduced. In order to accommodate jumpers of the same height with a jump rope tied to a fixed point at one end, the rope must be longer or the ends must be located closer together than with a rope rotated through an arc at both ends.
The primary problem associated with mechanically rotating a jump rope at both ends thereof relates to the synchronization of rotation at the two, opposite stations. Manually, it is not difficult for users to move in unison to swing a pair of ropes at a given frequency and phase angle. In order to repeat such motion by machine, the prior art has employed two separate methods. These two methods include mechanically gearing the first and second stations to the same motor, whereby both the opposite stations synchronously drive the ropes and the phase angle is set by the gear teeth. A scale model of such a device is disclosed in U.S. Pat. No. 1,893,173--Kreutzer. Alternatively, separate asynchronous drive means may be included for both stations, and the drive means put in such close control of the jumper that the jumper controls the speed and phase angle of the two independently-driven ends. In other words, the user is required to synchronize the power sources. This type of device appears in U.S. Pat. No. 3,107,092--Morris et al.
A rope swinging apparatus employing a common drive shaft or related gearing to synchronize the first and second stations is unduly expensive and complex for the usual playground application. A suitable rope swinging apparatus must be inexpensive enough to come within the usual cost for toys. Even where a playground or school elects to install a mechanical rope swinging apparatus, or if a unit is designed for a health spa or exercise salon, the common gearing or common drive shaft approach is too expensive and complex. The many mechanical parts required to mount the pair of driving stations at a fixed distance from one another, and the various bushings and shaft supports required, result in an enormously heavy and expensive device. Although this approach has been taken in a very small or scale model device (see U.S. Pat. No. 1,893,173--Kreutzer), the device is not practical if attempted in a full scale application.
Requirements such as shaft mountings and the like in a device having common gearing and drive result in further complexity when an attempt is made to design a device which will be at all versatile. For example, attempting a commonly-geared device wherein the rope swinging axis is adjustable to a plurality of heights (i.e., for a range of jumpers) requires that some apparatus be provided to commonly raise and lower both driving sides together. Such complexity is beyond the scope and resources of the usual user for such recreational equipment.
The present invention solves the difficulties of complexity by employing a driving station and a slave station, the slave station being freewheeling and driven only by the motion of the driving station, the driving force being transmitted through the jump rope. Accordingly, there is no requirement of mechanically synchronizing the speed and locking the phase angle of the two rope ends. The freewheeling driven station describes a more-natural rope motion than does a fixed end and a larger jumping area is provided. In a device adapted for swinging a pair of synchronized ropes, the dual shafts included in each station are synchronized with one another, however due to the freewheeling driven station, the driving and driven sides need not be mechanically attached to one another, other than through the jump ropes.
In addition to the more natural action and the fewer parts, the present device is also more compact than former devices, because instead of a fixed end, the narrowest radial span of the jump area is set by the rotating lever arms. Since complexity is minimal, additional features can be easily incorporated such as a height adjustment capability and interlocks to disconnect power in the event a jumper falls or becomes entangled in the ropes.